In industrialized, less temperate regions of the world, consideration has been given to techniques that would utilize the tremendous amount of low grade heat produced by conventional and nuclear power plants. Such low grade heat is contained in the cooling water supplied to the condensers of the power plants. Conventionally, river water is used as the heat sink of industrial power plants, and its temperature is raised, typically 5.degree.-10.degree. C., in the condenser system before the water is discharged downstream. Usually, the incremental heat added to the cooling water is wasted. Thus, although enormous amounts of heat are present in the discharge condenser cooling water, its low temperature, typically 15.degree.-30.degree. C., militates against its efficient utilization.
Using waste heat in a fluid, e.g., condenser cooling water whose thermal head is about 10.degree. C. or less, for industrial or residential heating purposes requires very efficient heat transfer equipment. One approach is to use a direct contact air-water heat exchanger located in an enclosure, e.g., a greenhouse. This will provide a very efficient transfer of heat from the condenser cooling water to the air in the greenhouse, but with an accompanying large increase in humidity within the greenhouse. Almost without exception, this approach will increase the humidity to a level that is unsuitable for plant growth, and uncomfortable or unhealthy for human habitation. Humidity can be controlled, however, and the heat contained in the low temperature fluid can be transferred to the air in a greenhouse by utilizing an indirect air-water heat exchanger, e.g., a shell and tube heat exchanger, located in the greenhouse. In this arrangement, condenser water flows through finned tubes over which forced air from the enclosure is blown. This approach to enclosure heating requires heat exchangers with large heat exchange surfaces because of the small thermal head involved, and requires the expenditure of large amounts of power to drive blowers for circulating air over the finned tubes with a velocity large to effect efficient heat transfer. Thus, size, complexity, and cost detrimentally affect the practicality of this approach to utilizing waste heat.
It is therefore an object of the present invention to provide a new and improved method of and apparatus for conditioning air in an enclosure which permits a reduction in physical size of the components, is more energy efficient, and yet permits both the humidity and temperature of the air in the enclosure to be maintained at predetermined levels.